Microplastics and emerging chemical contaminants in indoor dust: potential human exposure pathways and implications for food and human health

Introduction Indoor dust is increasingly recognised as an important medium for human exposure to microplastics and associated chemical contaminants. This study investigated the occurrence and characteristics of microplastics and emerging chemical contaminants in non-residential indoor environments and explored their potential implications for human exposure and food-chain transfer. Methods Indoor dust samples were collected from 600 non-residential environments across Kasaragod and Kannur districts, northern Kerala, using a passive deposition approach. Microplastics were quantified as deposition flux (particles/m²/day), and their morphology and polymer composition were examined using stereomicroscopy and Raman spectroscopy. Emerging chemical contaminants were screened using gas chromatography–tandem mass spectrometry (GC–MS/MS). Statistical analyses were performed to examine variations and associations among the investigated parameters. Results Microplastic deposition flux varied across indoor environments, with higher accumulation observed in settings associated with intensive human activity and material usage. Fibres were the dominant morphological type, followed by fragments and pellets. Raman analysis confirmed diverse polymer types, including polyethylene, polystyrene, polyester, polymethacrylates and polyhaloolefins. Several emerging chemical contaminant groups, including plasticizers, personal care product residues, hydrocarbons and aromatic compounds, were also detected. Statistical analysis revealed a strong positive association between microplastic deposition flux and emerging chemical contaminant occurrence. Principal component analysis further demonstrated co-occurrence patterns among microplastic characteristics and major contaminant groups. Discussion The findings highlight non-residential indoor dust as a potential pathway for simultaneous exposure to microplastics and associated chemical contaminants through hand-to-mouth transfer and deposition onto food and food-contact surfaces. They also underscore the importance of considering indoor dust in understanding potential human exposure and food-chain transfer pathways.